Ionic Compounds Flashcards
What is lattice energy?
The enthalpy change that accompanies the separation of 1 mol of an ionic solid into gaseous ions. It measures the strength of an ionic bond.
Is lattice energy always positive or negative?
Always positive
What is the Born-Haber Cycle?
A series of hypothetical steps and their enthalpy changes to convert elements to an ionic compound; it is used to calculate the lattice energy.
What are the 5 steps in the Born-Haber Cycle?
1) Vaporize the metal
2) Ionize the metal
3) Break the non-metal bond for diatomic species
4) Transfer electrons to the non-metal
5) Ions attract and form a compound
How do you use the Born-Haber Cycle to find lattice energy?
Use Hess’ Law to subtract the enthalpies of each step in the formation of an ionic compound from the enthalpy of the overall reaction.
The lattice energy is the opposite of the enthalpy of step 5 (forming a compound from the ions).
Is the formation of an ionic compound exothermic or endothermic?
Exothermic
Does lattice energy increase or decrease with greater ion size?
Lattice energy is lower in bigger ions.
This is because electrostatic attraction is greater in smaller ions since the charges are closer.
Does lattice energy increase or decrease with greater ion charge?
Lattice energy increases with higher ion charge.
This is because there is greater attraction between ions with higher charges.
What are 3 properties of ionic solids affected by lattice energy?
Melting point, hardness, and solubility
How does a high lattice energy impact the boiling and melting points of an ionic compound?
A high lattice energy means higher boiling and melting points.
When can ionic compounds conduct electricity?
When they are molten or dissolved.
Why do ionic compounds crack without deforming when force is applied?
Force disrupts the crystal lattice, pushing together ions with like charges. Subsequent repulsion causes cracking.
What is formed when ionic compounds are vaporized?
Ion pairs
